Adjust the atmosphere
Article label Article source: Combined cooling
Fruits and vegetables in tune with the concept of cold storage:
Normal air, usually containing 21% oxygen, 0.03% of carbon dioxide, the rest of the nitrogen and some trace gases. Fresh fruit is still a living body after life, in the storage process is still a normal respiration-oriented metabolic activities, mainly for the fruit consumption of oxygen, while the release of a certain amount of carbon dioxide and heat. In the environmental gas composition, carbon dioxide and the release of ethylene from the fruit have a significant effect on the respiration of the fruit.
Reduce the concentration of oxygen in the storage environment and increase the concentration of carbon dioxide, can inhibit the fruit respiration, thereby delaying the fruit ripening, aging, to extend the fruit storage period. Lower temperatures and hypoxia, high carbon dioxide can inhibit the synthesis of ethylene and weaken the ethylene to promote the aging of fruits, so as to reduce or avoid the occurrence of certain physiological diseases. In addition, the environment of a certain concentration of hypoxia, high carbon dioxide has the role of inhibition of fungal disease breeding and expansion.
Fruits and vegetables in tune with cold storage storage advantages:
(1) storage time long atmosphere storage integrated low temperature (cold storage) and adjust the storage environment of the two components of the gas technology, making fruit storage period to a large extent to extend. The use of modified atmosphere storage, the apple can be done on an annual basis; pear, long pear, pear and so on the use of modified atmosphere storage can be stored 8 to 9 months or more; gas storage storage kiwi longer than the storage period of 2 to 3 months the above.
(2) fresh effect of the majority of late-maturing apple and pear, long pear, pear and other fruits after long-term storage, still bright color, fruit green, pure flavor, full appearance, and just harvest when almost the same. Taking apple as an example, the flesh hardness, titratable acid and other indicators were significantly higher than those of cold storage during the same period.
(3) storage loss low air storage strict control of the library temperature, humidity and oxygen and carbon dioxide and other gas components, effectively inhibited the fruit's respiration, transpiration and microbial hazards, during storage due to loss of water, rot Loss greatly reduced. According to the Henan Institute of Biology on kiwi observation, in the same storage conditions, the average cold storage loss of up to 15% to 20%, while the total loss of less than 4% of the total storage. Hebei, a gas storage pear storage for 10 months, water loss rate is almost zero.
(4) shelf life Long after the storage of fruit due to long-term in the role of low oxygen and high carbon dioxide, in the lifting of the air conditioning state, there is still a long time "lag effect." According to the test on the apple in Shaanxi, it is generally believed that the shelf life of the atmosphere storage is 2 to 3 times that of the cold storage under the same quality.
(5) "green" storage in the fruit during the storage process, due to low temperature, low oxygen and relatively high carbon dioxide interaction, the basic can inhibit the occurrence of infectious diseases, the basic storage process without chemical anti-corrosion treatment The
Fruits and vegetables in tune with cold storage storage methods:
Modified atmosphere preservation method is currently the most common use of the international, the best, most advanced a fresh technology. Fruits and vegetables before and after picking are living organism, its internal a series of biochemical reactions, the most important of which is the role of breathing. Fruit and vegetable postharvest aerobic respiration is characterized by decomposition of fruits and vegetables stored in the cells of sugar, acid and other carbohydrates, resulting in carbon dioxide, water vapor, heat and some aromatic compounds, this process will consume fruit body, respiration The stronger, the faster the consumption, the sooner the finish, the shorter the storage time.
Affect the respiratory strength of the following factors:
Oxygen: storage space gas oxygen content, respiratory strength, otherwise less.
Carbon dioxide: storage of gas in the high concentration of carbon dioxide gas to inhibit breathing, delay the decomposition of pectin and chlorophyll degradation, and can inhibit microbial hazards, but too high will cause other physiological hazards to fruits and vegetables.
Temperature: storage space temperature decreases, respiratory strength decreased, otherwise increased, but too low (-1 ° C below) will produce frostbite.
In the atmosphere of fresh storage, depending on the different fruits and vegetables products set different air conditioning parameters: oxygen content is generally controlled in the range of 3% to 5%, carbon dioxide content control in the range of 1% to 8%, the temperature is generally controlled at -3 ~ 10oC range, the humidity is generally controlled in the range of 80% to 95%. It can be seen that the basic principle of the fresh-keeping technology is that according to the physiological characteristics of different fruits and vegetables products, the corresponding indicators, through the special test equipment and control equipment to control the storage environment of oxygen, carbon dioxide content, temperature, humidity, Temperature, delay the decomposition process, to maintain the original shape, color, flavor, texture and nutrition purposes.
Fruits and vegetables in tune with cold storage features:
Air conditioning library is developed on the basis of the traditional high temperature cold storage, from the surface it looks like a cold storage, but in the building structure and use management and high temperature cold storage is very different.
(1) airtight air tightness is the atmosphere of the library building requirements are different from the cold storage of a major feature. Air conditioning library requires the envelope structure should not only have insulation, moisture, reduce the exchange of hot and cold with the outside, but also requires the walls around the library, library doors and all the inlet and outlet connections strictly sealed, as much as possible to reduce the gas inside and outside the library exchange. Only in this way can artificially adjust the gas composition in the reservoir to reduce or avoid the interference of the outside gas to the gas composition in the reservoir.
(2) safety due to the atmosphere of the envelope on the envelope structure is more stringent, so in the cooling, gas transfer process, with the library temperature and pressure changes, will make the envelope on both sides of the pressure difference , Which will destroy the airtight layer, and even the envelope structure of the expansion or collapse. In order to balance and reduce the pressure inside and outside the library, air conditioning library must be equipped with safety valve and air bag.
(3) fast forward and out of the fruit into the state of the atmosphere as short as possible, the atmosphere of storage requirements of fruit storage fast, so as soon as possible to fill, close the door and gas. During the storage process as much as possible to reduce the number of open the door, frequent open the door not only affect the storage effect, increase operating costs, but also reduce the library door air tightness. Fruit out of the library, in order to ensure the shelf life of the fruit, the best one out or in the short term in batches.
(4) full of storage in addition to the necessary ventilation, check the channel, the library should be as high as possible full of full pile. On the one hand, due to the more fruit in the library, the less the porosity of the reservoir, and the less the consumption of oxygen in the fruit, the shorter the time the fruit enters the atmosphere; on the other hand, the larger the volume utilization factor, Can be reduced.
Citrus species and variety, since the fall to the next summer can be listed. Cultivation combined with storage and transportation, fresh fruit can be the annual supply. Citrus at room temperature has been stored throughout China's origin. Sweet orange or banana citrus large-scale storage for four months, can control the loss rate of less than 5%.
First, the variety and the storage environment requirements:
China's current cultivation of citrus varieties quite a lot of orange mainly orange, snow citrus, red orange (orange), orange (orange), orange, orange, orange and orange. Wide skin orange are mandarin orange, banana mandarin (barrels of mandarin, Zhaomeng), citrus, red orange, Nanfeng tangerine and so on. Pomelo has Shatian pomelo, grapefruit, white grapefruit, sesame oil and so on. Lemon with Beijing lemon (bergamot), the United States Yulik lemon.
Different types and varieties of citrus, the sensitivity of the great differences in temperature, which is the most low temperature is lemon, grapefruit, suitable for the storage temperature of 10-15 ℃; followed by pomelo, mandarin, suitable for the storage temperature 5-10 ℃; orange and sweet orange generally more resistant to low temperature, can tolerate low temperature of 1-5 ℃. However, some of the citrus orange can not tolerate low temperature, such as Guangdong citrus, suitable for the storage temperature of 10-12 ℃.
Second, the impact of citrus commodity quality factors:
1, sugar and acid ratio. The soluble solids content is 5-15% and the citric acid content is 0.3-1.2% between different species and varieties. In the storage process, citrus fruits continue to consume sugar and organic acids, at high temperatures, acid consumption more than sugar consumption. The quality of the fruit is not entirely dependent on the amount of solids contained in the mature, but depends on the sugar and acid ratio. Such as Wenzhou mandarin sugar and sour ratio of about 10: 1-13: banana mandarin for 12: 1-15: 1, sweet orange 30: 1-35: 1. Today's citrus market is more popular fruit is high, fresh color, juice and more, Sauvignon and high acid and high sugar flavor varieties.
2, dry disease. Dry water disease occurs mainly in the wide leather orange, the symptoms are peel foam, flesh separation, flesh dehydration, juice granulation, rough texture, flavor fades. In the orange also occurred, peel thick, rugged, white skin layer easy to peel, capsule wall thickening, hardening, transparency was white, juice cell dehydration, the fruit gradually lost flavor. The reasons for the production of dry water (floating skin) are related to the type of fruit. High temperature and high humidity during fruit ripening and high temperatures during storage will also promote the occurrence of low water. Some studies suggest that dry water is due to abnormal skin tissue aging.
3, brown spot and edema disease. Both of which are abnormal physiological conditions caused by low temperature. Brown spot fruit is outside the fruit in the outer skin appear irregular brown spots, the lesion of the oil cells rupture, so that the skin subsidence, with the disease development, lesion expansion or connected into a film, generally do not damage the pulp, The flavor is normal, but the appearance of the goods is greatly affected. The disease increased with time, weakened the fruit of the microbial invasion of resistance. Edema disease skin loss of the original luster, peel edema easily separated from the flesh, severe peel brown, flesh flavor.
4, mechanical damage. Citrus exocarp covered with oil cells, is a natural protective layer. Fresh fruit, exocarp bulge, extremely susceptible to mechanical abrasions or stab wounds. Harvesting or storage process, touch, hit, squeeze, pressure and drop caused by internal injuries, the naked eye is generally difficult to find, but the consequences are very serious, leading to rot.
5, other diseases. Citrus storage of microbial diseases are mainly green rot disease, black and brown pedicle rot, sour rot, black rot, brown rot and anthrax and so on. Tean, black rot, brown rot and anthrax are latent diseases, mostly in the late storage. And green green mold and sour rot mainly from the wound dip, mostly in the pre-storage disease.
Third, the storage technology of citrus:
1, harvest. Citrus fruit in addition to lemon must be timely harvest, usually in the fruit color area of 3/4, sugar and acid than to meet the standards should be harvested, followed by picking time is also very important, should avoid heavy rain or morning dew dry When the fruit. Harvesting staff must cut nails, bring gloves, to avoid injury; with round fruit cut, shoulder flattened under the scissors, a cut uneven to cut. Cut fruit people carry fruit bags, with the cut with the release. Packing box to add bedding, the fruit can not be loaded too full, so as not to crush, so the operator should be lightly put.
2, after the anti-corrosion measures. Postharvest timely use of fungicides for anti-corrosion treatment, to prevent the citrus in the storage of rotten very effective, commonly used fungicides are ceni Ling (bitter spirit), carbendazim, thiophanate spirit, Butylamine and 2,4-D) and methotrexate. The concentration of the fungicide was 0.05% -0.1% and the concentration of 2,4-D was 0.01% -0.025%. Harvest the best effect of the same day, in the post-harvest three days must be completed drug treatment. Fungicides can also be mixed with wax solutions or other coating agents.
3, selection and packaging. Long-term storage of citrus picking must be strictly removed after the injury, pests and diseases, no fruit, thick fruit and residual fruit, and then 0.01 mm thick polyethylene film single fruit packaging.
4, the appropriate storage method. (1) storage at room temperature. At room temperature storage is the main way of storage of citrus in China, such as well cellars, ventilation pits, air-raid shelters, and even relatively cool and ventilated ordinary houses can also store citrus. In Sichuan, a large number of sweet orange storage shelter, Nanchong area with a cellar storage of sweet orange, can also be stored to the second year of March to May, in the ordinary housing can be stored in the Spring Festival. At room temperature storage should pay attention to plastic film to do single fruit packaging and preservative treatment. (2) cold storage. In the relative humidity of 85-90% conditions, orange 3.5-9 ℃ can be stored for 2-4 months; wide leather orange 0-3.5 ℃ can be stored for 2-4 weeks. Cold storage is conducive to reducing rot and weight loss, but long-term low temperature storage must pay attention to avoid chilling injury, to prevent citrus produce brown spot and edema disease!
Strawberry fruit color red, water spirit, fruit soft and juicy, sweet and sour taste, containing calcium, phosphorus, iron and vitamin C and other rich nutrients. Strawberry water content is high, delicate organization, vulnerable to mechanical damage and microbial infection and rotten deterioration. At room temperature, the fruit placed 1 to 3 days began to change color, taste, it is difficult to store fresh. Researchers by the long-term practice and exploration, and finally worked out some strawberry storage and preservation methods. Now its technology is described as follows:
First, strawberry scientific harvesting technology
1, before harvesting strawberry harvesting with 0,1% to 0.5% of the calcium chloride solution spraying fruit, or after harvest with calcium chloride solution soaking, can inhibit the strawberries softening.
2, harvest time strawberry harvest the best in sunny days, strawberry first flowering fruit first mature, the entire harvest time lasted about 20 days, sub-batches of harvest, the general daily or the next day harvest once. Generally in the strawberry surface 3/4 color red when harvest is appropriate, premature harvest, fruit color and flavor are not good. Harvesting should be done after dew in the dew, and at high temperatures should be avoided at noon.
3, harvesting method strawberry peel is very thin, easy to damage damaged. Therefore, the harvest should be removed disease, bad fruit, the good berries gently placed in a special fruit plate, the fruit size to 90 cm x60 cm x15 cm as well, filled with strawberry fruit fruit can be set to polyethylene Sealed in the film bag, in time to send cold storage. You can also use a height of 3.0 cm within the hole basket harvest strawberries, put, avoid turning, to avoid touching the peel, the basket full of strawberries should be pre-cooling, the pharmaceutical treatment into the cold storage.
Second, strawberry scientific storage technology
1, the choice of storage and transportation of strawberry varieties of chicken heart, Shuo honey, lion head, Gorella, Po cross early, green seeds, Brandon Bao, Shanghai, Chunxiang, horses and other varieties intolerance storage and transportation. In the use of frozen storage preservation method, it is appropriate to use the meat of the dense treasure early, Brandonbao.
2, the drug fresh ① 0.05% sorbic acid soaking 2 to 3 minutes; ② peracetic acid fumigation treatment, according to the amount of 3cc per meter capacity 0.2 grams of peroxyacetic acid steaming for 30 minutes; Strawberry fruit is impregnated with sodium sulfite solution and dried. A mixture of 9 parts of sugar and 1 part of citric acid is placed in the bottom of a container, and the strawberry is stored thereon to significantly prolong the storage life. (4) Sulfur dioxide treatment. Strawberry into the plastic box, were placed 1 to 2 bags of sulfur dioxide chronic release agent, sealed with plastic box sealed, chronic sulfur dioxide release agent should keep a certain distance with the fruit.
3, storage method ① gas storage. A special fruit tray with good strawberries was collected and stored in an O.04 mm thick polyethylene film bag and sealed in an environment of 0 to 0.5 ° C and a relative humidity of 85 to 95%. Bag of oxygen accounted for 3% of carbon dioxide, carbon dioxide 6%, in this condition, the strawberry can be preserved for more than 2 months. Increase the concentration of carbon dioxide, decay rate greatly reduced, but the final concentration of carbon dioxide should not exceed 20%, or strawberry will produce alcohol flavor. ② cold storage. By gray mold infection, the fruit itself breathing strong, causing strawberry aging, leading to rot. Water evaporation caused by dehydration shrinkage, strawberry water loss of 5% of the loss of merchandise. Strawberry at room temperature, water loss, 2.17% ~ 2.65% per day, 3 to 4 days that the loss of commodity value, as well as the oxidation of fruit caused by color change is the main reason for the effect of strawberry preservation. Which reduces the temperature can effectively extend the storage time. Will be stored strawberry basket with a large plastic bag, tie the bag to prevent dehydration, dry shrink color, and then 0 ~ 3 ℃ in the cold storage, avoid the temperature fluctuated. ③ freezing point temperature storage strawberry freezing temperature is -0.77 ℃, strawberry is water evaporation and temperature independent fruit, even in the near freezing conditions, no packaging of strawberry water evaporation is also very intense. Therefore, small bags with plastic bags can improve the humidity of the surrounding environment, reduce air convection, inhibit evaporation, reduce weight loss. Respiration intensity is affected by the ambient temperature is very large, near the freezing point of the respiratory strength is room temperature conditions of 1/6, near freezing point storage of the specific conditions are: -0.5 plus or minus 0.2 ℃, relative humidity 85% to 90% Strawberry is stored in a 0.04 mm thick 30 cm x 32 cm polyethylene film bag,